Where Will the Band Go?

A snow day is possibly on tap for schools stretching from parts of northern Virginia to central New Jersey.  Energy from the northwest will sweep in and deepen off the coast of Delaware Tuesday.  With it will be the potential for plowable snow, especially in areas where the heaviest band sets up.

As of now, it is difficult to forecast exactly where that band will be – though many models have it parallel to the Mason-Dixon, wavering somewhere between 30 miles each way.  Even when that band sets up, warm air may hold strong and change snow over to rain.  This is especially true towards the south.

A good indicator at where the heavy precipitation will set up is the strongest vertical movement – upward.  Upward motion will move this moist air, cool it off, and condense the water vapor in the air to snowflakes and raindrops.  Look below at the vertical velocities from the NAM model – the strongest upward motion occurs south of the area.  Through central Maryland, central Delaware, and southern New Jersey.  And this is exactly where I believe the heaviest band of snow will form.

18Z-20160208_namNE_700_vvel

That said, it is generally very difficult to produce heavy snowfall from these types of systems.  The snow is often light and scattered (with the exception of the band).  And i’m not confident the snow will be as wide spread as what models indicate.

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The Calm Before the Blizzard of 2016

While the east coast braces itself for potentially one of the strongest storms on record, Winter Storm Watches and Blizzard Watches are starting to appear in the Mid-Atlantic.

Energy currently centered across the Rockies will continue to dip south, through the Tennessee Valley and make a turn towards the northeast.  That is where things get interesting…and difficult.  Where the storm heads from there – tracking close to the coast or further out to sea – will directly impact the amount of snow to fall across the region. Nonetheless, there will be times during this storm when blizzard-conditions will exist, especially across eastern Pennsylvania, New Jersey, and the Delmarva.  Blizzard conditions are defined as snow or blowing snow, winds in excess of 35 miles per hour and visibilities less than 1/4 of a mile all for 3 consecutive hours.

Models continue to fluctuate in and out of consensus with each other, with most dropping over a foot of snow along the I-95 corridor from Washington DC to Philadelphia. While there are many factors that favor this heavy, historic thumping, snow lovers should be warned of two potential buzz-kills.

Areas of red show warming air about a mile up in the atmosphere.  This could translate to a layer above freezing, thus melting the snow before it hits the ground.

Areas of red show warming air about a mile up in the atmosphere. This could translate to a layer above freezing, thus melting the snow before it hits the ground.

First off, is the dreaded rain-snow line.  As the surface low develops to the east of the Delmarva, strong easterly winds will drive onshore.  With sea surface temperatures approaching 50 degrees, warm waters will heat up the shallow layer of air and change the snow over to rain for much of New Jersey, Delaware, the eastern shore of Maryland, and even into southeastern Pennsylvania. In addition, incredibly strong winds whipping from the south around the area of low pressure will produce a warm surge that will support this potential changeover.

A depiction of a dry slot getting wrapped into the system. These areas see significantly less precipitation than most other areas.

A depiction of a dry slot getting wrapped into the system. These areas see significantly less precipitation than most other areas.

A second limitation to watch out for is the development of a dry slot. Dry slots are areas of dry air that get wrapped within the storm, and generally seen in nor’Easters.  If verified, this would greatly reduce the potential snowfall for this system across these areas.

While snow totals may underachieve in some areas and exceed expectations in others, there is no doubt power outages will be a major concern.  Heavy wet snow built up on branches will snap and trees may all-out topple over in sustained winds of 30 miles per hour gusting to 60 miles per hour.

Now my thoughts…. Exactly predicting a dry slot is like nailing Jell-O to the wall.  Until the system forms, and approaches the region, it is very difficult to tell if the dry slot will form and where this will be.  I do think much of the area within 100 miles of the coast will switch over to rain or sleet.  Further west, a deformation band – an enhanced area of snow – will form….that will be the big money winner.


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Early Look at this Weekends Possible Snow

You may have already heard much of the east coast may see its first decent snowfall of the year towards the end of this week.  And while the possibility is certainly there for this, it is far from set in stone.

Here’s what we know…

1) Energy currently in the middle of the north Pacific will slide towards the United States and enter somewhere around Oregon or Washington state.  It will then dip down across the Rockies. This energy powers the storm – it gives it the low the dynamics it needs to crank up.

vort 1-20 1am vort 1-21 7am vort 1-22 7pm

blockinglow2) The speed of the system.  This is not absolutely set in stone yet, but there is a good deal of consensus across all of the models that low pressure off the coast of Greenland, would serve as a block from this low getting out of the area at any high speed rate.  Longer duration storm = more cold air = higher snow totals.

2mt 1-21 4pm2) Cold temps? You got it.  Surface temperatures below freezing cover the entire northeast and some of the mid-atlantic.  As the storm approaches, much of the area will have temperatures cold enough to support snowfall.

What we don’t know…

Screen Shot 2016-01-18 at 10.20.58 AM1) As with virtually all weather systems 5 days out, the path of the system is up in the air.  A track up the Appalachians and it’s a soggy weekend for most as warm air gets pulled inland and changes any snow to rain.  A track out to sea and the cold air maintains, but any snowfall stays suppressed south.  A happy medium is needed for a decent snowfall.

2)The intensity.  There are many thermodynamic and dynamic properties drive the intensity of nor’easters.  None of which can be concluded this far out.

3) Snow totals.  Any sites posting totals are estimates based on long range projections.  It’s like trying to predict the score of a football game between two teams 3 years away.  Serves zero value, and normally very inaccurate.

There’s still 5 days before the storm has the potential to have an impact on the east – way too much time for variances in the track, intensity, and other variables.   I’ll update as the week goes on to zero in on the possibility of snow and how much to expect.

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